THE HIGH PRICE of commonly used medications for conditions like asthma contributes heavily to health care costs in the United States.

Drugs account for 10 percent of the country's $2.7 trillion annual health bill, even though the average American takes fewer prescription medicines than people in France or Canada, said Gerard Anderson, who studies medical pricing at the Bloomberg School of Public Health at Johns Hopkins University.

Being able to afford prescription medications in America often requires top-notch insurance or plenty of disposable income, and time to hunt for deals.

And unlike other countries, where the government directly or indirectly sets an allowed national wholesale price for each drug, the United States leaves prices to market competition among pharmaceutical companies, including generic drug makers.

But competition is often a mirage in today's health care arena — a surprising number of lifesaving drugs are made by only one manufacturer — and businesses often successfully blunt market forces.